The present invention relates to an image processing program, and an image processing system using this program, and in particular relates to a game program which enables reduction of the processing load for shadow texturing in a game system, which is one mode of such an image processing system.
In a game system which is one mode of an image processing system, model-type shadows (hereafter simply called “humanoid shadows”) of humans, animals, fantasy creatures, robots, and similar are displayed, accompanying characters displayed on a display screen (representing objects which perform fighting in an action game) and moving in accordance with character movements.
Drawing of such humanoid shadows is achieved by performing calculations and creating shadow texture for each frame, based on the character model and on the motion thereof, and then applying this to a polygon constituting the surface. At this time, calculations and creation must be performed for the number of characters to be displayed on one screen.
Hence the greater the number of characters to be displayed in one screen of an action game or similar, the greater is the load on the drawing processor which performs drawing processing.
Thus in drawing character shadows, as the number of characters displayed within one screen increases, the load of character motion calculations and shadow model drawing increases, and occurrence of incomplete processing increase.
One conceivable method for dealing with this problem is to simplify the form of the shadow to be drawn, employing for example approximate shadows. When drawing with approximate shadows, a shadow texture is not generated, so that there is no load resulting from shadow texture generation.
However, if approximate shadows are used uniformly, then approximate shadows are drawn as shadows for drawings when characters have fallen down and in similar cases, imparting a sense of unnaturalness to the game player.
As a method of forming shadows in a game system, the technology disclosed in Japanese Patent Laid-open No. 2002-190032 is known. The invention disclosed in this patent reference has the characteristic that shadows formed by a character itself are generated and displayed in realtime when projecting shadows of the character onto other portions.
Further, the invention disclosed in this Japanese Patent Laid-open No. 2002-190032 makes no mention of a solution to the problem, described above, in which the greater the number of characters displayed on one screen, the greater is the load on the drawing processor to perform drawing.